And JAL's main domestic competitor, All Nippon Airways, is much further down the road of cooperating with one of those U.S. companies, setting the stage for a smoother ramp-up of their own closer marketing agreement later this year.

Conversations with advisers to several potential candidates suggest that the first reason for the slow ramp-up is a basic one: The coming campaign isn't for an open seat in the White House, but rather will be a race against an incumbent president.